Soluble nanoparticles for composite performance enhancement

ABSTRACT

A composition may include a resin and a plurality of polymer nanoparticles in the resin to form a resin mixture. The polymer nanoparticles may be soluble or semi-soluble in the resin. At least partial dissolution of the polymer nanoparticles may result in the alteration of one or more of the properties of the resin.

FIELD

The present disclosure relates generally to composite materials and,more particularly, to the use of nanoparticles in composite structures.

BACKGROUND

The manufacturing of a composite structure may include applying uncuredresin to reinforcing fibers of a composite layup. The temperature of thecomposite layup may be increased to reduce the viscosity of the resin sothat the resin may flow and infuse into the fibers. The composite layupmay be held at an elevated temperature for a predetermined period oftime to cure the resin into a solidified or hardened state. After theresin has cured, the composite structure may be passively or activelycooled to ambient temperature.

In many composite material systems, the resin may have a coefficient ofthermal expansion (CTE) that may be different than the CTE of thereinforcing fibers. For example, epoxy resins may have a CTE that may bean order of magnitude greater than the CTE of carbon fibers. Thedifference in CTE may result in the resin and fibers contracting bydifferent amounts as the composite structure cools down from the curingtemperature. The difference in contraction of the resin relative to thefibers may result in thermally-induced stresses in the resin. Thethermally-induced stresses may result in undesirable microcracking inthe resin. Microcracking may also occur during the service life of acomposite structure due to changes in temperature of the operatingenvironment of the composite structure. In addition, microcracking mayoccur near the outer regions of a composite structure in response toimpact with an object

Prior art attempts to reduce or prevent microcracking include theaddition of tougheners to liquid resin. Conventional thermoset resinsmay be formed using liquid polymers to form an uncured liquid resin.Alternatively, solid polymers may be dissolved into liquids duringmixing to form an uncured liquid resin. Tougheners in liquid or solidform may be added to the uncured liquid resin to improve the resistanceof the resin to microcracking. Unfortunately, adding tougheners to resinmay result in a reduction in the final resin glass transitiontemperature during curing, or the tougheners may increase the curetemperature of the resin and/or cause excessive cure shrinkage of theresin.

In addition, tougheners often increase the viscosity of the resin whichmay impair manufacturability and thus effectively limit the amount oftoughener that can be added to the resin. Advanced thermoset resinstypically require relatively high cure temperatures (e.g., 350-600° F.)to fully cure the thermoset resin/composite. Such high cure temperaturesmay result in increased thermally-induced stresses and strains due tothe differential CTE between the fibers and resin.

As can be seen, there exists a need in the art for a system and methodfor improving the toughness and other properties of a resin such as fora composite structure.

SUMMARY

The above-noted needs associated with resins are specifically addressedby the present disclosure which provides a composition that may includea resin containing a plurality of polymer nanoparticles to form a resinmixture. The polymer nanoparticles may be soluble or semi-soluble in theresin. The full or partial dissolution of the polymer nanoparticles mayresult in the alteration of one or more of the properties of the resinmixture.

Also disclosed is a composite structure which may include a resin, aplurality of polymer nanoparticles in the resin to form a resin mixture,and a plurality of reinforcing fibers embedded within the resin mixture.At least a portion of the polymer nanoparticles may be soluble orsemi-soluble in the resin may result in or cause an improvement in oneor more of the properties of the resin and/or the composite structure.

Additionally disclosed is a method of manufacturing a composition. Themethod may include mixing soluble and/or semi-soluble polymernanoparticles into a resin to form a resin mixture. The method mayadditionally include curing the resin mixture, and at least partiallydissolving the polymer nanoparticles in the resin prior to or during thecuring of the resin.

The features, functions and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments, further details of whichcan be seen with reference to the following description and drawingsbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent upon reference to the drawings wherein like numbers refer tolike parts throughout and wherein:

FIG. 1 is a block diagram of a composite structure including reinforcingfibers and a resin mixture comprising resin containing polymernanoparticles;

FIG. 2 is a perspective view of a composite structure including a stackof unidirectional plies each formed of a plurality of continuousreinforcing fibers;

FIG. 3 shows a cross-section of a portion of a composite structureshowing reinforcing filaments of the unidirectional plies oriented atdifferent angles;

FIG. 4 is an enlarged view of a portion of the composite structure takenalong line 4 of FIG. 3 and showing a plurality of polymer nanoparticlesin the resin;

FIG. 5 is a schematic illustration of an uncured resin mixture takenalong line 5 of FIG. 4 and illustrating a plurality of fully-solublepolymer nanoparticles in the resin mixture;

FIG. 5A is a schematic illustration of the cured resin mixture of FIG. 5showing substantially complete dissolution of the fully-soluble polymernanoparticles into the resin;

FIG. 6 is a schematic illustration of an uncured resin mixture showing aplurality of semi-soluble polymer nanoparticles in the resin mixture;

FIG. 6A is a schematic illustration of the cured resin mixture of FIG. 6showing the partial dissolution of the semi-soluble polymernanoparticles in the resin;

FIG. 6B is a schematic illustration of a semi-soluble polymernanoparticle of FIG. 6A and schematically illustrating a gradient oftoughness extending from a particle center toward the base resinsurrounding the semi-soluble polymer nanoparticle;

FIG. 7 is a schematic illustration of an uncured resin mixtureillustrating a plurality of semi-soluble polymer nanoparticles in theresin mixture;

FIG. 7A is a schematic illustration of the cured resin mixture of FIG. 7showing the partial dissolution of the semi-soluble polymernanoparticles in the resin and further showing each semi-soluble polymernanoparticles maintaining a pure nanoparticle core;

FIG. 7B is a schematic illustration of a semi-soluble polymernanoparticle of FIG. 7A and schematically illustrating a gradient oftoughness extending from the pure nanoparticle core to the base resinsurrounding the semi-soluble polymer nanoparticle;

FIG. 8 is a schematic illustration of an uncured resin mixtureillustrating a plurality of core-sheath nanoparticles in the resinmixture with each core-sheath nanoparticle having a sheath encapsulatinga core;

FIG. 8A is a schematic illustration of the cured resin mixture of FIG. 8showing the dissolution of the sheaths into the resin such that only thecore remains after curing of the resin;

FIG. 9 is a schematic illustration of an uncured resin mixturecontaining a plurality of two different types of polymer nanoparticles;

FIG. 9A is a schematic illustration of the cured resin mixture of FIG. 9showing the partial dissolution of the two different types of polymernanoparticles in the resin and resulting in a gradient of toughnessaround the location of each polymer nanoparticle;

FIG. 10 is a schematic illustration of an uncured resin mixturecontaining a plurality of core-sheath nanoparticles each having asoluble sheath encapsulating a shaped particle;

FIG. 10A is a schematic illustration of the cured resin mixture of FIG.10 after dissolution of the sheaths such that the shaped particlesremains in the resin;

FIG. 11 through 21 are non-limiting examples of different configurationsof shaped particles that may be encapsulated in a core-sheathnanoparticle;

FIG. 22 is a schematic illustration of an uncured resin mixturecontaining a plurality of core-sheath nanoparticles randomly oriented inthe resin mixture;

FIG. 22A is a schematic illustration of an electrical or magnetic fieldapplied to an uncured resin mixture containing core-sheath nanoparticlesencapsulating shaped particles and showing the active alignment of theparticle axes with electrical or magnetic field lines;

FIG. 22B is a schematic illustration of core-sheath nanoparticles in anuncured resin mixture and showing the shaped particles oriented alongtwo different directions;

FIG. 22C is a schematic illustration of core-sheath nanoparticles in anuncured resin mixture and showing some of the shaped particles orientedalong two different directions in response to an electrical or magneticfield, and some of the shaped particles being randomly oriented;

FIG. 23 is a schematic illustration of shaped particles oriented along acommon direction to influence the direction of the propagation of acrack;

FIG. 24 is a flowchart illustrating one or more operations that may beincluded in a method of manufacturing a composition;

FIG. 25 is a flowchart illustrating one or more operations that may beincluded in a method of redirecting a crack in a composite structure.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various embodiments of the disclosure, shown in FIG. 1 is ablock diagram of a composite structure 100 including a composition 110.The composition 110 may include a resin mixture 114. In some examples,the composition 110 may include further include reinforcing fibers 118.The reinforcing fibers 118 may be made up of a plurality of reinforcingfilaments 120. The resin mixture 114 may include resin 112 containingpolymer nanoparticles 200. The polymer nanoparticles 200 may be solubleor semi-soluble in the resin 112. In some examples, the polymernanoparticles 200 may be fully-soluble in the resin 112. In otherexamples, the polymer nanoparticles 200 may be partially soluble in theresin 112. The dissolved portion of the polymer nanoparticles 200 may becured or solidified during the resin cure or solidification cycle.

The dissolution of the fully-soluble or semi-soluble polymernanoparticles 202 (FIG. 5), 204 in the resin 112 may result in animprovement in the properties of the resin 112 and/or an improvement inthe properties or performance of a composite structure 100 manufacturedwith the resin 112 (FIG. 2) containing the polymer nanoparticles 200.For example, the partial or complete dissolution of polymernanoparticles 200 in the resin 112 may result in an increase in thetoughness of the resin 112 in one or more regions of the resin 112 or inone or more regions of a composite structure 100 (FIG. 2) containing theresin 112. An increase in the toughness of the resin 112 may reduce orprevent crack (not shown) initiation or growth within the resin 112. Inother examples, the partial or complete dissolution of polymernanoparticles 200 in the resin 112 may result in increased flammabilityresistance and/or reduced smoke and/or toxicity of the resin 112 and/orof a composite structure 100. Additional improvements that may beprovided by addition of the polymer nanoparticles 200 to the resin 112may include increased corrosion resistance, increased electricalconductivity, reduced cure-shrinkage-related distortion, reducedheat-of-reaction-related resin degradation, reducedcure-shrinkage-related distortion, improved modulus of elasticity, andan increase in the strength and/or strain properties of resin 112 or ina composite structure 100 containing the resin 112.

The polymer nanoparticles 200 may also cause one or more properties of aresin 112 or composite structure 100 to be non-isotropic. In thisregard, dissolution of polymer nanoparticles 200 in a resin 112 (FIG. 2)may cause the toughness, coefficient of thermal expansion (CTE),stiffness (e.g., modulus), strength, conductivity (electrical orthermal), and/or failure strain of the resin 112 to have differentvalues along different directions of the resin 112. For example,dissolution of polymer nanoparticles 200 (FIG. 2) may result in themodulus or failure strain of the resin 112 to be higher along adirection transverse to reinforcing fibers 118 relative to the modulusor failure strain of the resin 112 along a direction non-transverse toreinforcing fibers 118 (FIG. 2). Advantageously, the polymernanoparticles 200 may be provided in a wide range of materials which mayallow for the ability to alter or improve the properties of the resin112 and/or composite structure 100 over wide range of property values.

In addition, the polymer nanoparticles 200 may be provided in arelatively small size which may allow the resin mixture 114 (FIG. 5) toretain a relatively low viscosity even at high load levels of thepolymer nanoparticles 200 in the resin 112. For example, the polymernanoparticles 200 may be provided in a cross-sectional width 206 (FIG.5) or particle diameter of approximately 10-200 nanometers. In someexamples, the polymer nanoparticles 200 may have a cross-sectional width206 of between 10-100 nanometers. Advantageously, a relatively smallcross-sectional width of the polymer nanoparticles 200 may prevent thereinforcing filaments 120 or fibers 118 (FIG. 2) from filtering outoverly-large nanoparticles such as during prepregging operations orduring the process of infusing resin 112 into the fibers 118 of acomposite layup 102 (FIG. 2). In this regard, an overly-largecross-sectional width of the polymer nanoparticles 200 may preventpassage of the polymer nanoparticles 200 between adjacent reinforcingfilaments 120 and/or between adjacent fiber tows. In some examples, thepolymer nanoparticles 200 may be provided in different cross-sectionalwidths or diameters which may enable different volumetric ratios ofresin-to-nanoparticles within a resin mixture 114 or within a compositelayup 102.

The polymer nanoparticles 200 may be provided in a generally rounded orspherical shape to retain a relatively low viscosity at high polymernanoparticle load levels, and to avoid interlocking of nanoparticleswith other nanoparticles or with fibers 118 or filaments 120 (FIG. 2) asmay otherwise occur with non-spherical or complexly-shaped nanoparticlesthat have sharp edges or corners. The polymer nanoparticles 200 may beconfigured to retain their rounded or spherical shape up to a certainpoint during the cure cycle and/or prior to complete or partialdissolution of the polymer nanoparticles 200 in the resin 112. Forexample, the polymer nanoparticles 200 (FIG. 2) may retain their roundedor spherical shape at least up to the glass transition temperature ofthe resin 112 and/or below the cure temperature of the resin 112.

Advantageously, by retaining their generally rounded or spherical shapebelow a predetermined temperature, the polymer nanoparticles 200 mayremain entrained within the resin mixture 114 (FIG. 2) as the resinflows through and infuses a composite layup 102. It should be noted thatthe polymer nanoparticles 200 are not limited to generally rounded orspherical shapes. For example, polymer nanoparticles 200 (FIG. 2) may beprovided in an oblong or elliptical shape, or in three-dimensionalshapes such as cylinders, tube, cubes, rectangles, pyramids, and othershapes. The relatively small cross-sectional width 206 (FIG. 5) and/orthe generally rounded shape (e.g., spherical) of the polymernanoparticles 200 may allow for a relatively high concentration ofpolymer nanoparticles 200 within the resin 112 with a relatively smallincrease in resin viscosity.

In some examples, the polymer nanoparticles 200 may constitute up to 75percent by volume of a resin mixture 114 containing resin 112 andpolymer nanoparticles 200. Preferably, the polymer nanoparticles 200 mayconstitute a minimum of 10 percent by volume of a resin mixture 114 asthe low end of a range of volumetric percentage of polymer nanoparticles200. However, in some examples, the polymer nanoparticles 200 mayconstitute no less than 5 percent by volume at the low end of the range.In still other examples, the polymer nanoparticles 200 may constitute noless than 10 percent by volume of the resin mixture 114 at the low endof the range. In further examples, the polymer nanoparticles 200 mayconstitute no less than 15 percent by volume at the low end of therange.

In certain applications, it may be desirable to provide the polymernanoparticles 200 at a maximum of 65 percent by volume of a resinmixture 114 as a high end of a range of percentage by volume of polymernanoparticles 200. However, in some examples, the polymer nanoparticles200 may constitute no more than 50 percent by volume as the high end ofthe range. In certain applications, polymer nanoparticles 200 may beprovided in any combination of the above-mentioned low end and high endof the range of volumetric percentage of polymer nanoparticles 200 of aresin mixture 114. Non-limiting examples of combinations of theabove-mentioned low end and high end of a range of percentage by volumeof polymer nanoparticles 200 include an arrangement wherein the polymernanoparticles 200 constitute from 5-75 percent by volume of a resinmixture 114. Another example may include polymer nanoparticles 200 thatconstitute from 10-75 percent by volume of a resin mixture 114. In stillother examples, the polymer nanoparticles 200 may constitute from 15-65percent by volume of a resin mixture 114. In an even further example,the polymer nanoparticles 200 may constitute from 20-50 percent byvolume of a resin mixture 114. Advantageously, the generally rounded orspherical shape of the polymer nanoparticles 200 allows for linearimprovements in the resin 112 properties with linear increases in theconcentration level of polymer nanoparticles 200 in the resin 112 withminimal or negligible effect on resin viscosity.

The polymer nanoparticles 200 may be included in a resin mixture 114 forany one of a variety of different applications including, but notlimited to, adhesives, coatings, plastics for injection molding, a resinfor fiber-reinforced composite structures 100 (FIG. 2), and otherapplications. The polymer nanoparticles 200 (FIG. 2) may be included inthermosetting resins 112 and in thermoplastic resins 112. In addition,the polymer nanoparticles 200 may be used in pre-impregnatedfiber-reinforced layups and in dry fiber layups. The polymernanoparticles 200 may also be used in a variety of resin systemsincluding, but not limited to, resin film infusion, vacuum assistedresin transfer molding, and other systems for infusing dry fiberpreforms 124 (FIG. 2) with resin 112.

FIG. 2 shows a composite structure 100 made up of a stack of compositeplies 104. In the example shown, each one of the composite plies 104 maybe a unidirectional ply 108. Each one of the unidirectional plies 108(FIG. 3) may include a plurality of parallel, continuous reinforcingfibers 118 or fiber tows which may be configured as unidirectional tape122 or unidirectional sheet. Each one of the fiber tows may be made upof a bundle of several thousand reinforcing filaments 120. For example,a single fiber tow may include up to 100,000 or more reinforcingfilaments 120. In some examples, a reinforcing filament may have afilament cross-sectional width or diameter of 5-30 microns. For example,a carbon reinforcing filament may have a filament cross-sectional widthof approximately 5-7 microns. Glass reinforcing filaments may have afilament cross-sectional width of 10-25 microns. In the presentdisclosure, the terms reinforcing fiber, fiber tow, and composite fibermay be used interchangeably. Reinforcing fibers 118 for use in acomposite layup 102 (FIG. 3) may be provided in any one of a variety ofdifferent fiber forms, and are not limited to unidirectional tape 122 orunidirectional sheet. For example, a composite structure 100 may beformed of composite plies 104 (FIG. 3) configured as woven fabric,braided fibers, stitched fiber forms, chopped fibers in fiber mats, andany one of a variety of crimp and non-crimp fiber forms.

The composite structure 100 of FIG. 2 may be formed by stacking dryfiber composite plies 104 which may be later infused with resin 112. Forexample, a liquid resin mixture 114 (FIG. 2) containing polymernanoparticles 200 may be infused into a dry fiber composite layup 102after which heat and/or pressure may be applied to consolidate and cureor solidify the composite layup 102 (FIG. 3) to form a compositestructure 100. In some examples, the dry fiber composite layup 102 maybe infused with unmodified resin. In the present disclosure, unmodifiedresin may be described as resin 112 that does not contain polymernanoparticles 200, or is devoid of polymer nanoparticles 200.

After infusing the composite layup 102 with unmodified resin, polymernanoparticles 200 may be applied to one or more locations of thecomposite layup 102 prior to consolidating and curing or solidifying thecomposite layup 102 (FIG. 3) to form a composite structure 100. Forexample, a solution of polymer nanoparticles 200 may be uniformlyapplied throughout a composite layup 102. Alternatively, polymernanoparticles 200 may be provided in a higher concentration in a firstregion 220 (FIG. 4) of a resin mixture 114 or composite structure 100,and a lower concentration of polymer nanoparticles 200 in a secondregion 222 (FIG. 4) of the resin mixture 114 or composite structure 100.In this manner, the resin mixture 114 or composite structure 100 mayhave different properties in the first region 220 relative to theproperties of the resin mixture 114 (FIG. 2) or composite structure 100in the second region 222. The types of properties that may be differentin a first region 220 relative to a second region 222 may includetoughness, modulus, strength, failure strain, coefficient of thermalexpansion (CTE), flammability resistance, smoke and toxicity levels,electrical conductivity, corrosion resistance, cure shrinkage, heat ofreaction, and other properties.

For example, a solution of polymer nanoparticles 200 may be applied toincrease the resin toughness in specific locations of a composite layup102, such as in the interlaminar regions 106 between selected compositeplies 104 (FIG. 2), and/or between opposing side edges of fiber tows ortape of one or more composite plies 104, while remaining regions of acomposite structure 100 may be devoid of polymer nanoparticles 200. Insome examples, a solution of polymer nanoparticles 200 (FIG. 2) may beapplied to resin-rich pockets of a composite layup 102. Resin-richpockets may be described as high-resin-content locations in a compositelayup 102 (FIG. 2), or locations that have a large volume of resinrelative to the volume of fibers. A resin mixture 114 containing polymernanoparticles 200 may be infused into a dry fiber composite layup 102such that the polymer nanoparticles 200 are substantially uniformlydistributed in bulk throughout the composite layup 102.

Advantageously, the relatively small size of the fully-soluble orsemi-soluble polymer nanoparticles 202, 204 allows for substantiallyuniform dispersion of the dissolved nanoparticle material within theresin at the location each nanoparticle. More specifically, therelatively small size of the nanoparticles (e.g., 10-200 nm) results ina relatively short path length (e.g., on the order or nanometers) forthe dissolved nanoparticle material to mix with the resin at the(former) location of each nanoparticle. For example, in arrangementswhere fully-soluble or semi-soluble polymer nanoparticles 202, 204 areuniformly dispersed throughout a composite layup, the small size of thenanoparticles 202, 204 results in substantially uniform distribution ofthe dissolved nanoparticle material within the resin throughout thecomposite layup resulting in uniformity in the improved properties ofthe resin throughout the composite structure. Likewise, in arrangementswere fully-soluble or semi-soluble polymer nanoparticles 202, 204 arelocally applied to targeted regions such as between composite plies,between opposing side edges of side-by-side fiber tows, and/or inresin-rich pockets, the small size of the nanoparticles 202, 204 allowsfor a substantially uniform distribution of the dissolved nanoparticlematerial within the resin at the targeted regions and resulting inuniformity in the improved properties of the resin and/or compositestructure at such targeted regions.

A composite structure 100 may also be formed by laying up a stack ofcomposite plies 104 that may be pre-impregnated (e.g., prepreg compositeplies) with a resin mixture 114 containing polymer nanoparticles 200.After laying up the stack of prepreg composite plies, heat and/orpressure may be applied to consolidate and cure or solidify thecomposite layup 102 to form a composite structure 100. In otherexamples, the prepreg composite plies may be pre-impregnated withunmodified resin, and polymer nanoparticles 200 may be selectivelyapplied to target regions of a composite layup 102 (FIG. 2) such as theabove-mentioned high-resin-content locations of a composite layup 102.Alternatively, the polymer nanoparticles 200 may be substantiallyuniform distributed in bulk throughout a composite layup 102. Forexample, a solution of polymer nanoparticles 200 (FIG. 2) may be applieduniformly throughout the composite layup 102, or in selected areas ofthe composite layup 102. Even further, a film of resin (not shown)containing polymer nanoparticles 200 may be laid up between one or moredry fiber composite plies 104 (FIG. 2) or between one or more prepregcomposite plies of a composite layup 102. Polymer nanoparticles 200 mayalso be applied to reinforcing filaments 120 during manufacturing and/orprepregging of the reinforcing filaments 120.

In any one of the examples disclosed herein, the resin 112 and/orpolymer nanoparticles 200 (FIG. 2) may be formed from thermoplasticmaterial and/or thermosetting material. Thermoplastic material mayinclude at least one of the following: acrylics, fluorocarbons,polyamides, polyolefins (e.g., polyethylenes, polypropylenes),polyesters, polycarbonates, polyurethanes, polyaryletherketones (e.g.,polyetheretherketone (PEEK), polyetherketoneketone (PEKK),polyetherketoneetherketone (PEKEK)), etc.), and polyetherimides.Thermosetting material may include at least one of the following:polyurethanes, phenolics, polyimides, sulphonated polymer (polyphenylenesulphide), a conductive polymer (e.g., polyaniline), benzoxazines,bismaleimides, cyanate esthers, polyesters, epoxies, andsilsesquioxanes. The reinforcing filaments 120 or reinforcing fibers 118may be formed from materials such as carbons, silicon carbide, boron,ceramic, and metallic material. The reinforcing filaments 120 or fibers118 (FIG. 2) may also be formed from glass such as E-glass(alumino-borosilicate glass), S-glass (alumino silicate glass), puresilica, borosilicate glass, optical glass, and other glass compositions.

A resin mixture 114 may contain polymer nanoparticles 200 formed of twodifferent materials. In this regard, some of the polymer nanoparticles200 in a resin mixture 114 may have a different material compositionthan other polymer nanoparticles 200 in the same resin mixture 114. Thedifferent materials of the polymer nanoparticles 200 may provide a meansfor altering the properties of the resin 112 (FIG. 2) and/or compositestructure 100 in different ways, as described below. In another example,some of the polymer nanoparticles 200 in a resin mixture 114 may becore-sheath nanoparticles 240 having a sheath 242 encapsulating a core244 (FIG. 8). The core 244 may have a material composition that may bedifferent than the material composition of the sheath 242. In someexamples, the core 244 may have a spherical shape with a cross-sectionalwidth of 10-200 nanometers. In some examples, the core 244 may be ashaped particle 246 or a non-spherical particle, as described below.

FIG. 3 shows a cross-section of a portion of the composite structure 100of FIG. 2, and illustrating the reinforcing filaments 120 that make upthe fibers 118 or unidirectional tape 122 of the composite plies 104. Inthe example shown, the reinforcing filaments 120 in the uppermost andlowermost composite plies 104 are oriented along a directionperpendicular to the plane of the paper. The middle two composite plies104 of the composite layup 102 in FIG. 3 include reinforcing filaments120 that are oriented parallel to a plane the paper. The composite plies104 located between the middle and uppermost composite ply 104 andbetween the middle and lowermost composite ply 104 contain reinforcingfilaments 120 oriented non-parallel and non-perpendicular to the planeof the paper. However, the reinforcing filaments 120 in any one of thecomposite plies 104 may be arranged in any orientation, withoutlimitation.

FIG. 4 shows a portion of the composite structure 100 of FIG. 3 andillustrating the plurality of polymer nanoparticles 200 substantiallyuniformly dispersed throughout the resin mixture 114. As indicatedabove, the composite plies 104 may be formed of pre-impregnatedunidirectional tape 122 containing polymer nanoparticles 200. Afterlayup of the composite plies 104, heat and/or pressure may be applied toreduce the viscosity of the pre-impregnated resin 112, allowing theresin 112 (FIG. 3) to flow and intermingle with the resin 112 ofadjacent composite plies 104 such that the polymer nanoparticles 200 maybecome substantially uniformly distributed throughout the compositelayup 102. However, as indicated above, a composite layup 102 may beformed of composite plies 104 that may be pre-impregnated withunmodified resin. Polymer nanoparticles 200 may be applied to specificlocations of the composite layup 102 such as by spraying a solution onresin-rich pockets associated with the composite layup 102. For example,polymer nanoparticles 200 may be applied to the interlaminar regions 106between one or more pairs of adjacent composite plies 104. In anotherexample, polymer nanoparticles 200 may be applied between the side edgesof adjacent fibers 118 or tapes of a composite layup 102.

In still other examples, polymer nanoparticles 200 may be applied in amanner such that the nanoparticles are predominately located within afiber bed, and the remainder of the composite layup 102 (FIG. 4) such asthe interlaminar regions 106 may be devoid of polymer nanoparticles 200.Further in this regard, polymer nanoparticles 200 may be selectivelyapplied to one or more of the outer surfaces (not shown) of a compositelayup 102 to provide targeted functionality. For example, polymernanoparticles 200 (FIG. 4) may be applied to the external surfaces orregions of a composite layup 102 that may interface with a metalliccomponent (not shown). In some examples, the polymer nanoparticles 200may include tougheners that may improve the impact resistance of theouter region of a composite structure 100 (FIG. 4), or the polymernanoparticles 200 may reduce or prevent fatigue-induced propagation ofmicrocracks (not shown) that may occur near the outer regions of acomposite structure 100 in response to impact with an object. Polymernanoparticles 200 may also be applied to other locations of a compositelayup 102 to improve the resistance to initiation or propagation ofmicrocracks in the resin 112.

In an example not shown, polymer nanoparticles 200 may be applied towoven fabric (not shown) or braided fibers (not shown) such as inresin-rich pockets at the divots (not shown) formed at the intersectionsof intersecting fiber tows of woven fabric or braided fibers. Evenfurther, polymer nanoparticles 200 may be selectively applied to certainregions of a composite layup 102 (FIG. 4) such as thicker sections(e.g., containing a larger quantity of composite plies 104) of acomposite layup 102, while thinner sections of a composite layup 102(e.g., containing a smaller quantity of composite plies 104) may bedevoid of polymer nanoparticles 200. As described below, selectivelyapplying polymer nanoparticles 200 may locally increase the toughness ofthe resin 112 (FIG. 3) at the location of the polymer nanoparticles 200which may prevent or reduce crack growth or crack initiation at suchlocations. By reducing the propensity for crack growth or crackinitiation in one or more locations of a composite structure 100, theload-carrying capability of the composite structure 100 (FIG. 4) may beincreased which may allow for a reduction in the structural mass of thecomposite structure 100. A reduction in the structural mass may provideperformance advantages. In the case of an aircraft, a reduction instructural mass may correspond to an increase in fuel efficiency, range,payload capacity, or other performance improvements.

FIG. 5 is a schematic illustration of an uncured resin mixture 114containing a controlled number of polymer nanoparticles 200. In theexample shown, the polymer nanoparticles may be fully-soluble 202 in theresin 112. The fully-soluble polymer nanoparticles 202 may besubstantially uniformly disbursed within the resin 112 such that theviscosity of the resin mixture 114 is controlled by the viscosity of theresin 112. However, for any one of the polymer nanoparticleconfigurations disclosed herein, different areas of a composite layup102 may be provided with different load levels of polymer nanoparticles200. For example, polymer nanoparticles 200 may be applied only toresin-rich pockets of a composite layup 102, as indicated above.Alternatively, polymer nanoparticles 200 may be applied in differentload levels at different location along the length, width, and/orthickness of a composite layup 102.

FIG. 5A is a schematic illustration of the cured resin mixture 114 ofFIG. 5 showing the substantially complete dissolution of thefully-soluble polymer nanoparticles 202 into the resin 112, andresulting in a generally homogenous composition 110 of resin 112 (FIG.5) and dissolved polymer nanoparticle material. In some examples, thefully-soluble polymer nanoparticles 202 may remain in a solid statebelow a predetermined temperature of the resin 112 and/or for apredetermined period of time, and may dissolve in the resin 112 abovethe predetermined temperature and./or after a predetermined period oftime. For example, any one of the polymer nanoparticles 200 (FIG. 5)disclosed herein may be configured to retain a substantially rounded orspherical shape during resin flow and/or infusion through the compositelayup 102, and the polymer nanoparticles 200 may dissolve after themajority of the resin flow has occurred. The point at which the polymernanoparticles 200 dissolve may be controlled by tailoring the solubilityof the polymer nanoparticle material composition, and/or by tailoringthe cure cycle such as the hold time(s) and associated temperature(s) ofthe cure cycle.

As a result of the substantially complete dissolution of thefully-soluble polymer nanoparticles 202, the properties of the resin 112may be improved, as indicated above. The type of properties that may beimproved in the resin 112 (FIG. 5) may depend upon the materialcomposition of the polymer nanoparticles 200. For example, the fulldissolution of fully-soluble polymer nanoparticles 202 may result in asubstantially uniform increase in the toughness of the resin 112 whichmay advantageously reduce or prevent crack initiation or crack growthwithin the resin 112. Other properties that may be improved upondissolution of the fully-soluble polymer nanoparticles 202 (FIG. 5) mayinclude increased flammability resistance, reduced smoke, reducedtoxicity of the resin 112 and/or composite structure 100. Thedissolution of the fully-soluble polymer nanoparticles 202 may alsoresult in increased electrical conductivity, reducedcure-shrinkage-related distortion, reduced heat-of-reaction-relateddistortion, and reduced heat-of-reaction-related resin degradation inthe final composite structure 100.

FIG. 6 is a schematic illustration of an uncured resin mixture 114containing a plurality of semi-soluble polymer nanoparticles 204. Asindicated above, the quantity of polymer nanoparticles 200 in the resin112 may be controlled to provide a precisely-controlled concentrationlevel of polymer nanoparticles 200 in the resin 112. As in thefully-soluble polymer nanoparticles 202 shown in FIG. 5, thesemi-soluble polymer nanoparticles 204 in FIG. 6 may be substantiallyuniformly disbursed within the resin 112. The semi-soluble polymernanoparticles 204 may be configured to remain in a solid state andthereby retain their spherical shape below a predetermined temperatureof the resin 112. For example, in any the embodiments disclosed herein,the semi-soluble or fully-soluble polymer nanoparticles 202, 204 may beconfigured to remain in a solid state below the glass transitiontemperature of the resin 112, such that the polymer nanoparticles 200may remain entrained within the resin 112 during the majority of thetime that the resin 112 is flowing within the composite layup 102.

FIG. 6A is a schematic illustration of the cured resin mixture 114 ofFIG. 6 showing the partial dissolution of the semi-soluble polymernanoparticles 204 into the resin 112. The semi-soluble polymernanoparticles 204 may be configured to partially dissolve in the resin112 above a predetermined temperature such as above the glass transitiontemperature of the resin 112. The point during the curing cycle when thesemi-soluble polymer nanoparticles 204 start to dissolve may becontrolled by the material composition of the semi-soluble polymernanoparticles 204, or by controlling the curing process parameters suchas the temperature and time associated with the curing cycle. Thepartial dissolution of the semi-soluble polymer nanoparticles 204 mayresult in a gradient 214 of properties around the location of each oneof the semi-soluble polymer nanoparticles 204.

FIG. 6B schematically illustrates a semi-soluble polymer nanoparticle204 of FIG. 6A and shows a gradient 214 of one or more propertiesextending from a particle center 210 toward the cured base resin 112surrounding the semi-soluble polymer nanoparticle 204. The base resin112 may retain its original chemistry around the semi-soluble polymernanoparticle 204. In one example, the partial dissolution of asemi-soluble polymer nanoparticle 204 may a result in a gradient 214 oftoughness that extends from the particle center 210 toward the baseresin 112 surrounding the location of the semi-soluble polymernanoparticle 204. In some examples, the toughness may be highest nearthe particle center 210 due to a higher concentration of the originalpolymer nanoparticle material at the particle center 210. The toughnessmay gradually decrease along a direction toward the base resin 112surrounding the semi-soluble polymer nanoparticle 204. Advantageously,by at least partially dissolving the semi-soluble polymer nanoparticle204 in the resin 112 to create a gradient 214 of properties, anotherwise abrupt or sharp interface between the base resin 112 andnon-soluble polymer nanoparticle (not shown) may be avoided which maythereby avoid stress concentrations where microcracking may initiate orpropagate.

As may be appreciated, semi-soluble polymer nanoparticles 204 may alsobe at least partially dissolved in a resin 112 to result in propertygradients 214 (FIG. 6A) other than toughness. For example, partialdissolution of semi-soluble polymer nanoparticles 204 may result inlocal gradient 214 s of elastic modulus, strength, strain-to-failure,cure shrinkage, heat of reaction, coefficient of thermal expansion(CTE), flammability resistance, smoke and/or toxicity release, and anyone of a variety of other mechanical properties.

FIG. 7 is a schematic illustration of an uncured resin mixture 114containing semi-soluble polymer nanoparticles 204 in the resin mixture114. FIG. 7A is a schematic illustration of the cured resin mixture 114of FIG. 7 showing the partial dissolution of the semi-soluble polymernanoparticles 204 in the resin 112. The result of the partialdissolution of the polymer nanoparticles 200 in FIG. 7A is similar tothe partial dissolution of semi-soluble polymer nanoparticles 204 inFIG. 6A, with the exception that in FIG. 7A, a pure nanoparticle core212 remains at the location of each semi-soluble polymer nanoparticle204.

FIG. 7B schematically illustrates the semi-soluble polymer nanoparticles204 of FIG. 7A and showing a gradient 214 of toughness extending fromthe pure nanoparticle core 212 of each semi-soluble polymer nanoparticle204 to the base resin 112 surrounding the semi-soluble polymernanoparticle 204. As indicated above, the material composition of thepolymer nanoparticles 200 may be selected to alter or improve one ormore specific properties of the resin 112, and are not limited toimproving toughness the resin 112.

FIG. 8 is a schematic illustration of an uncured resin mixture 114containing a plurality of core-sheath nanoparticles 240. Eachcore-sheath nanoparticle 240 may include a sheath 242 encapsulating acore 244. The sheath 242 may be formed of a different material than thecore 244. The sheath 242 may be soluble in the resin 112 such that onlythe core 244 remains after the resin 112 cures. The core 244 may beformed of insoluble material. In some examples, the sheath 242 may besemi-soluble in the resin 112 such that the sheath 242 adhesively bondsthe core 244 to the cured resin 112 without the use of reactive speciesthat may undesirably generate heat.

FIG. 8A is a schematic illustration of the cured resin mixture 114 ofFIG. 8 showing the dissolution of the sheaths 242 into the resin 112such that only the cores 244 remain after the resin 112 cures. Thematerial composition of the core 244 may be selected to improve one ormore specific properties of the resin 112, and which may be differentthan the resin 112 properties that may be improved by dissolution of thesheath 242 (FIG. 8). The core 244 may be formed of any material fromwhich the resin 112 may be formed. The core 244 may be formed of amaterial composition that has a reduced cure shrinkage relative to theresin cure shrinkage, a reduced heat of reaction relative to the resinheat of reaction, a reduced coefficient of thermal expansion (CTE)relative to the resin CTE, or any one of a variety of other propertiesincluding, but not limited to, any of the above-mentioned propertyimprovements or performance advantages provided by polymer nanoparticles200 (FIG. 8). The at least partial dissolution of the sheath 242 mayresult in a gradient 214 of mechanical properties extending from aparticle center 210 toward the base resin 112, as described above forthe examples in FIGS. 5-7B.

FIG. 9 is a schematic illustration of an uncured resin mixture 114containing a plurality of two different types of polymer nanoparticles200. One or more of the polymer nanoparticles 200 may be formed of afirst nanoparticle material 216, and one or more of the polymernanoparticles 200 may be formed of a second nanoparticle material 218which may have different properties than the first nanoparticle material216. The polymer nanoparticles 200 may be configured as fully-solublepolymer nanoparticles 202 (FIG. 5) and/or as semi-soluble polymernanoparticles 204. In the example shown, the polymer nanoparticles 200are configured as semi-soluble polymer nanoparticles 204.

FIG. 9A is a schematic illustration of the cured resin mixture 114 ofFIG. 9 showing the partial dissolution of the two different types ofsemi-soluble polymer nanoparticles 204 in the resin 112 and resulting ina gradient 214 of toughness around the location of each semi-solublepolymer nanoparticles 204. The polymer nanoparticles 200 may beconfigured such that at potentially different points during the curecycle, the semi-soluble polymer nanoparticles 204 may at least partiallydissolve into the resin 112. As discussed above, the points at which thepolymer nanoparticles 200 dissolve may be controlled by configuring thesolubility or material composition of each type of semi-soluble polymernanoparticles 204. In one example, the dissolution of the semi-solublepolymer nanoparticles 204 and the subsequent curing of the resin 112 mayresult in a resin mixture 114 that may be toughened with a controllednumber of polymer nanoparticles 200 that may each have a gradient 214 oftoughness around the location of each semi-soluble polymer nanoparticle204. The resin 112 may maintain its original chemistry around thelocation the semi-soluble polymer nanoparticles 204.

The selection of the chemistry and quantity of the semi-soluble polymernanoparticles 204 provides a means to create a multi-phase resin whereinthe size and properties of the different phases of the resin 112 can becontrolled. For example, adding 20 weight % of a thermoset polyimidecore and soluble high molecular weight thermoplastic polyimde sheathnanoparticle to an epoxy resin will result in a multiphase resincontaining an epoxy phase and discrete epoxy-polyimide blend phasessurrounding nanoscopic polyimide phases. In contrast, adding 75 weight %of the thermoset polyimide core and soluble high molecular weightthermoplastic polyimde sheath nanoparticle to an epoxy resin will resultin a multiphase resin containing small/localized epoxy phases between alarge epoxy-polyimide blend phases surrounding nanoscopic polyimidephases.

FIG. 10 is a schematic illustration of an uncured resin mixture 114containing a plurality of core-sheath nanoparticles 240 each having asheath 242 encapsulating a shaped particle 246 or a non-sphericalparticle. The shaped particle 246 may be insoluble in the resin 112. Thesheath 242 may be soluble and may be generally rounded or spherical asdescribed above to improve the dispersion capability of the core-sheathnanoparticles 240 within the resin 112 and to minimize effects on resinviscosity. The core-sheath nanoparticles 240 may be used in any of theabove-described implementations of polymer nanoparticles 200. Forexample, core-sheath nanoparticles 240 may be included in adhesives,coatings, plastics for injection molding, resins 112 for compositelayups 102 (FIG. 4), and any applications. The sheath 242 of thecore-sheath nanoparticles 240 may be provided in the sizes (e.g.,between 10-200 nm), load levels (e.g., up to 75 percent by volume of aresin mixture 114), and may be formed of any one of the above-describedmaterials for polymer nanoparticles 200. Core-sheath nanoparticles 240may be applied to resin 112, to fibers 118, and/or to a composite layup102 using any of the above-described techniques for applying polymernanoparticles 200 to resin 112, fibers 118 (FIG. 2), and compositelayups 102. For example, core-sheath nanoparticles 240 may be applied totapes, fabrics, braids, chopped fiber mats, and any one of a variety ofother fiber forms during prepregging operations. In another example, asolution of core-sheath nanoparticles 240 may be selectively applied totarget locations of a dry fiber composite layup 102 in the same manneras described above for applying polymer nanoparticles 200.

Although FIG. 10 illustrates shaped particles 246 in a bow tieconfiguration, shaped particles 246 may be provided in any one of avariety of sizes, shapes, and configurations to achieve specificfunctionalities of a resin 112 such as to direct the propagation ofcracks (FIG. 23) as discussed below, and/or to improve specificproperties of a resin 112. For example, the shaped particles 246 may beelectrically conductive to improve the charge distribution capability ofa composite structure 100 as may be desirable in the event of alightning strike. The shaped particles 246 may also cause one or moreproperties of a resin 112 to be non-isotropic. For example, shapedparticles 246 in a resin 112 may cause the coefficient of thermalexpansion (CTE), the stiffness (e.g., modulus), the strength, theconductivity (electrical or thermal), and/or the failure strain of theresin 112 to have different values along different directions of theresin 112 to achieve certain design requirements. In the example offailure strain, the shaped particles 246 may be configured and activelyoriented in a manner that results in a greater failure stain of theresin 112 along a direction transverse to a lengthwise direction of thereinforcing fibers 118 (FIG. 2), and a lower failure stain of the resin112 along directions non-transverse to the lengthwise direction of thereinforcing fibers 118.

FIG. 10A is a schematic illustration of the cured resin mixture 114 ofFIG. 10 after dissolution of the sheaths 242 during the cure cycle suchthat only the shaped particles 246 remain after the resin mixture 114cures. Advantageously, the dissolved sheath 242 may adhesively bond thecore 244 (FIG. 10) to the cured resin 112 without the use of reactivespecies that may undesirably generate heat. Dissolution of the sheath242 within the resin 112 may result in a significant increase in thetoughness of the resin mixture 114 similar to the above-describedtoughness increase provided by the at least partial dissolution ofpolymer nanoparticles 200. Advantageously, by using a spherically-shapedsheath, the shaped particles 246 may be uniformly distributed within theresin 112 (FIG. 10) without agglomeration during resin flow, and withoutsignificantly increasing resin viscosity. The shaped particles 246 maybe formed of any one of a variety of materials including, but notlimited to, metallic material, polymeric material, and inorganicmaterial including ceramics and glasses. In some examples, the shapedparticles 246 may be formed of the same material as the resin 112 andmay be at least partially cured prior to curing of the resin mixture114.

The sheath 242 of the core-sheath nanoparticles 240 may be formed of adifferent material than the sheath 242 of other core-sheathnanoparticles 240 in the resin mixture 114. For example, the sheath 242(FIG. 10) of some of the core-sheath nanoparticles 240 may be formed ofa material that locally increases the toughness of the resin 112, andthe sheath 242 of other core-sheath nanoparticles 240 in the same resinmixture 114 (FIG. 10A) may be formed of a different material whichimproves the stiffness or modulus of the resin 112 or provides otherimprovements to the properties of the resin 112. A single core-sheathnanoparticle 240 may contain two or more shaped particles 246 which maybe shaped the same as one another, or the shaped particles 246 (FIG.10A) may have different shapes. Multiple shaped particles 246 in asingle core-sheath nanoparticle 240 may be formed of the same materialor of different materials. For example, a resin mixture 114 may includecore-sheath nanoparticles 240 each having two or more shaped particles246 in each core-sheath nanoparticle. Some of the core-sheathnanoparticles 240 (FIG. 10) in the resin mixture 114 may include oneshaped particle 246 formed of metallic material to improve theelectrical conductivity of the resin mixture 114, and another shapedparticle 246 may be formed of ceramic material to reduce the net cureshrinkage of the resin mixture 114.

FIG. 11 through 21 are non-limiting examples of different configurationsof shaped particles 246 that may be encapsulated in a core-sheathnanoparticle. For example, FIG. 11 illustrates a toroid configuration,FIG. 12 illustrates a disk with a hole, FIG. 13 illustrates a cylinder,FIG. 14 illustrates a bow tie, FIG. 15 illustrates a jack configuration,and FIG. 16 illustrates a cross. FIG. 17 illustrates a cross having acentral mass, FIG. 18 illustrates a 4-point star, FIG. 19 illustrates a6-point star, FIG. 20 illustrates a triangle configuration, and FIG. 21illustrates a dog bone configuration. Any one or more of the shapes maybe provided as thin plates or the shapes may have varying thicknesses.For example, a triangle shaped particle may be provided as a thin plateor as a pyramid. A square shaped particle may be provided as a thinplate or as a cube, etc. As may be appreciated, the shaped particles 246may be provided in any one of a variety of different shapes andconfigurations, without limitation. The size and configuration of ashaped particle 246 may be selected to provide desired effects on one ormore properties of the resin 112 (FIG. 10).

FIG. 22 is a schematic illustration of an uncured resin mixture 114containing a plurality of core-sheath nanoparticles 240. In the exampleshown, the shaped particles 246 each have a bow tie configuration,although the shaped particles 246 may be provided in any one of avariety of different configurations, as indicated above. Each one of theshaped particles 246 has a particle axis 248 which is shown extendingalong a lengthwise direction of the bow tie configuration. In FIG. 22,the particle axes 248 of the shaped particles 246 are randomly orientedin the resin mixture 114.

FIG. 22A is a schematic illustration of a device that may be implementedfor orienting the particle axes 248 of the shaped particles 246. In theexample shown, the device includes a spaced pair of elements 250 whichmay be configured as bars or plates positioned in spaced relation to oneanother. A potential difference or charge may be applied across theelements 250 to generate an electrical and/or magnetic field across theresin mixture 114. In some examples, diametrically opposite sides of theshaped particles 246 may be oppositely charged along the particle axes248. The application of the potential difference across the spaced pairof elements 250 may cause rotation of the core-sheath nanoparticles 244(FIG. 22) until the particle axes 248 align with the magnetic fieldlines 252, and which may result in the particle axes 248 to be orientedgenerally parallel to one another as shown. The application of thepotential difference across the elements 250 may be applied during a lowviscosity portion of the cure cycle to allow the core-sheathnanoparticles 240 to easily rotate into the desired orientation.Advantageously, the spherical shape of the sheath 242 (FIG. 22) provideslittle resistance to the rotation of the core-sheath nanoparticles 240within the uncured resin. Such resistance to rotation may otherwiseoccur if the shaped particles 246 were non-encapsulated by a sphericalsheath.

FIG. 22B is a schematic illustration of core-sheath nanoparticles 240 inan uncured resin mixture 114 and showing the shaped particles 246oriented along two different directions. In the example shown, theshaped particles 246 may be configured such that upon application of anelectrical and/or magnetic field, the shaped particles 246 are activelyoriented into specific directions. FIG. 22C illustrates a plurality ofcore-sheath nanoparticles 240 in an uncured resin mixture 114 andshowing some of the shaped particles 246 oriented along two specificdirections in response to the application of an electrical or magneticfield, and additionally showing some of the shaped particles 246 thatare non-responsive to the electrical and/or magnetic field and thusremaining randomly oriented.

FIG. 23 is a schematic illustration of shaped particles 246 orientedalong a common direction to illustrate the influence of the orientationof the shaped particles 246 on the propagation of a crack 116 in theresin 112 (FIG. 22). In the example shown, each shaped particle 246 hasa particle axis 248 extending along a lengthwise direction of the shapedparticle 246. Opposite ends of the shaped particles 246 may beoppositely charged such that upon application of an electrical and/ormagnetic field, the particle axis 248 (FIG. 22C) are oriented intoalignment with the magnetic field lines 252, as described above. In someexamples, the shaped particles 246 may directly influence thepropagation of a crack 116 by altering the path of the crack 116. Inother examples, the shaped particles 246 (FIG. 22B) may indirectlyinfluence the propagation of a crack 116 by the changing the propertiesof the resin 112 in different directions as result of the presence ofthe shaped particles 246 in the resin 112. For example, a crack 116 maypreferentially progress along a direction where the crack 116 overcomesthe local failure strain of the resin 112 in response to local stresses.

FIG. 24 is a flowchart illustrating one or more operations that may beincluded in a method 300 of manufacturing a composition 110. Step 302 ofthe method may include mixing polymer nanoparticles 200 such as solubleand/or semi-soluble polymer nanoparticles 202 (FIG. 5), 204, 200 into aresin 112 to form a resin mixture 114 (FIG. 5). As indicated above, thepolymer nanoparticles 200 may be mixed into any one of a variety ofdifferent thermosetting or thermoplastic resins 112. In addition, thepolymer nanoparticles 200 may be provided in any one of a variety ofdifferent thermosetting and/or thermoplastic materials. In someexamples, the polymer nanoparticles 200 may be formed of the samematerial as the resin 112 (FIG. 5) and may be partially or fully curedor solidified prior to the curing of the resin 112. In addition, polymernanoparticles 200 formed of one material and/or size may be mixed withthe resin 112 with polymer nanoparticles 200 formed of other materialsand/or sizes. Providing polymer nanoparticles 200 (FIG. 5) of differentmaterials and/or sizes in the same resin mixture 114 may provide a meansfor tailoring the material composition of the resin 112 to achievedifferent properties in the resin 112. For example, polymernanoparticles 200 formed of a material for increasing the toughness of aresin 112 may be provided in relatively greater quantity and in largersizes than other polymer nanoparticles 200 that may be added to theresin 112 for the purpose of increasing the modulus of the resin 112.

Step 304 of the method 300 may include infusing reinforcing fibers 118(FIG. 2) with the resin mixture 114 prior to curing the resin mixture114. As indicated above, polymer nanoparticles 200 may be added to aresin mixture 114 during prepregging operations for prepregging any oneof a variety of fiber forms. For example, polymer nanoparticles 200 maybe mixed with a resin 112 to form a resin mixture 114 (FIG. 2) which maythen be applied to any one of a variety of fiber forms (e.g., fibertows, unidirectional tape, woven fabric, braided fibers, etc.) duringprepregging operations. The prepreg fiber forms may then be laid up ascomposite plies 104 in a stacked formation to which heat and/or pressuremay be applied to consolidate and cured or solidify the resin 112 toform a composite structure 100. In another example, one or more dryfiber preforms 124 (FIG. 2) may be laid up in a stacked formation afterwhich the layup may be infused with resin 112 containing polymernanoparticles 200. The resin-infused layup may then be consolidatedand/or cured or solidified to form a composite structure 100. In stillother examples, resin films (not shown) containing polymer nanoparticles200 may be laid up between one or more prepreg composite plies or dryfiber composite plies followed by the application of heat and/orpressure to cure and/or solidify the resin 112 (FIG. 2) to form acomposite structure 100. Other techniques are available for applyingpolymer nanoparticles 200 to a resin mixture 114. It should also benoted that the present disclosure contemplates forming compositionscontaining polymer nanoparticles 200 in resin 112, and wherein thecomposition 110 is devoid of reinforcing fibers. For example, polymernanoparticles 200 in resin 112 may be used as coatings, adhesives,injection moldable plastics, and other applications.

In some examples, the method may include mixing into the resin 112 twodifferent types of polymer nanoparticles 200 such as a first polymernanoparticle type (not shown) and a second polymer nanoparticle (notshown). The dissolution of the first polymer nanoparticles and/or thesecond polymer nanoparticles may result in resin properties that aredifferent than the properties of resin lacking first and/or secondpolymer nanoparticles. In some examples, the dissolution of the firstpolymer nanoparticle type may result in different properties in theresin 112 (FIG. 10) relative to the resin properties resulting from thedissolution of the second polymer nanoparticle type. Further thisregard, three or more types of polymer nanoparticles 200 may be mixed ina resin 112 to achieve distinct properties in the resin 112. Forexample, one type of polymer nanoparticle 200 may include a catalystthat may dissolve in the resin 112 and promote the cross-linkingreaction of thermosetting resin 112. A second type of polymernanoparticle 200 may be a core-sheath nanoparticle 240 having shapedparticles 246 (FIG. 10A) to control the propagation of cracks 116 in theresin 112. A third type of polymer nanoparticle 200 may be formed of amaterial that has a higher toughness in the resin 112 such that upondissolution of the toughening polymer nanoparticle 200 (FIG. 10), theresin mixture 114 has a higher net toughness than the base resin 112.

In another embodiment, different concentrations of polymer nanoparticles200 may be applied to different locations or regions of a compositelayup 102. In this regard, the method may include adding a higherconcentration of polymer nanoparticles 200 to a first region 220 of theresin 112 (FIG. 5) relative to the concentration of polymernanoparticles 200 added to a second region 222 of the resin 112, andgenerating different properties of the resin 112 in the first region 220relative to the properties of the resin 112 in the second region 222(FIG. 4) as a result of the higher concentration of polymernanoparticles 200 in the first region 220 relative to the concentrationof polymer nanoparticles 200 (FIG. 4) in the second region 222. Forexample, a higher concentration of polymer nanoparticles 200 may beadded to the interlaminar region 106 between one or more of thecomposite plies 104 of composite layup 102. Remaining regions of thecomposite layup 102 (FIG. 4) may receive a lower concentration ofpolymer nanoparticles 200 relative to the interlaminar regions 106, orthe remaining regions may be devoid of polymer nanoparticles 200.

Step 306 of the method 300 may include curing or solidifying the resinmixture 114. As indicated above, thermosetting resin 112 (FIG. 6) may becured by the application of heat and/or a catalyst to initiate thecross-linking reaction for curing the thermosetting resin 112. Hardenermay also be added to promote the cross-linking reaction. A compositelayup 102 (FIG. 2) containing thermoplastic resin 112 may be formed bypassively or actively reducing the temperature of the thermoplasticresin 112 below the glass transition temperature.

Step 308 of the method 300 may include at least partially dissolving thepolymer nanoparticles 200 in the resin 112 prior to or during the curingor solidifying of the resin 112. In some examples, the method mayinclude fully dissolving polymer nanoparticles 200 in the resin 112prior to or during curing or solidifying of the resin 112 (FIG. 8). Inother examples where the polymer nanoparticles 200 are semi-solublepolymer nanoparticles 204, the method may include partially dissolvingthe polymer nanoparticles 200 such that a gradient 214 of mechanicalproperties may be formed between a particle center 210 and the baseresin 112 surrounding the location of each semi-soluble polymernanoparticle 204. In some examples, the polymer nanoparticles 200 may becore-sheath nanoparticles 240 including a soluble or semi-soluble sheath242 encapsulating an insoluble core 244. In some examples, the core 244(FIG. 8) may be formed as a shaped particle 246 (FIG. 10A) as describedabove. The at least partial dissolution of the sheath 242 mayadvantageously result in a gradient 214 of properties around the shapedparticle 246. In addition, the partial dissolution of the sheath 242 mayresult in the non-reactive bonding of the core 244 or shaped particle246 to the resin 112 during curing of the resin 112.

Prior to or during the process of curing the resin 112, the method mayinclude maintaining the polymer nanoparticles 200 in a generally solidstate for a predetermined time and below a predetermined temperatureduring the curing cycle, and increasing the rate at which the polymernanoparticles 200 (FIG. 9) dissolve with an increase in temperature andtime that the polymer nanoparticles 200 are in the resin 112. In thisregard, the material composition of the polymer nanoparticles 200 and/orthe cure cycle parameters including the cure temperatures and cure timesmay be controlled to control the amount of time during which the polymernanoparticles 200 remain in a generally solid state. For example, it maybe desirable that the polymer nanoparticles 200 retain a generally solidstate and a generally spherical shape throughout the initial processingof a composite layup 102 (FIG. 4) including during injection or infusionof resin 112 (FIG. 9) into the layup, during vacuum bagging, duringconsolidation, and/or during other points or the resin cure cycle.Following the majority of resin flow, the polymer nanoparticles 200 maybe configured to dissolve at a desired point during the cure cycle suchas below the gel point of the resin 112. By ensuring that the polymernanoparticles 200 dissolve to the desired extent prior to a certainpoint during curing such as prior to the gel point, the resin 112 mayhave enough mobility to ensure dissolution of the polymer nanoparticles200.

In some examples, the method may include mixing core-sheathnanoparticles 240 in a resin 112, and then dissolving the sheath 242prior to or during the curing of the resin mixture 114 such that onlythe shaped particles 246 (FIG. 22A) remain in the resin mixture 114. Themethod may include rotating at least some of the polymer nanoparticles200 into a desired orientation of the shaped particles 246 relative toat least one common direction prior to curing the resin mixture 114(FIG. 22). For example, an electrical and/or magnetic field may beapplied to a resin mixture 114 containing core-sheath nanoparticles 240and causing rotation of the nanoparticles until the particle axes 248(FIG. 22) of the shaped particles 246 are in alignment with the fieldlines 252 of the electrical and/or magnetic field lines 252. In someexamples, the method may include aligning the particle axes 248 of aplurality of shaped particles 246 along a specific direction as a meansto redirect the propagation of a crack 116 in the resin 112, asdescribed above.

Step 310 of the method may include improving one or more mechanicalproperties of the resin mixture 114 as a result of at least partiallydissolving the polymer nanoparticles 200 in resin 112. Properties thatmay be improved as a result of dissolution of the polymer nanoparticles200 in resin 112 (FIG. 22) may include an improvement in the toughness,modulus, strength, failure strain, electrical or thermal conductivity,and/or any one or more of the above-described properties of a resin 112.For examples where the polymer nanoparticles 200 are at leastpartially-dissolved within the resin 112 including the sheath 242 (FIG.22) of core-sheath nanoparticles 240 (FIG. 22), the method may includecausing the formation of a gradient 214 of mechanical properties aroundlocations of at least partially dissolved polymer nanoparticles 200. Themechanical properties for which a gradient 214 (FIG. 6A) may be formedmay include many of the above-described properties. In some examples, atleast partial dissolution of the polymer nanoparticles 200 may result inany one or more of the above-described properties being non-isotropic inthe resin 112. For example, at least partial dissolution of one or morepolymer nanoparticles 200 may result in the failure strain of the resin112 along one direction to be greater than the failure strain of theresin 112 along another direction.

FIG. 25 is a flowchart illustrating one or more operations that may beincluded in a method 400 of redirecting a crack 116 (FIG. 23) in acomposite structure 100 (FIG. 2). The composite structure 100 may becomprised of a resin mixture 114 (FIG. 23) including resin 112 (FIG. 1)containing a plurality of polymer nanoparticles 200 (FIG. 1). Fibers 118may be embedded in the resin 112. At least some of the polymernanoparticles 200 may initially be provided in the resin 112 ascore-sheath nanoparticles 240 (FIG. 1). Each one of the core-sheathnanoparticles 240 may have a soluble sheath 242 encapsulating anon-soluble core 244 which may be formed as a shaped or non-sphericalparticle 246 (FIG. 23). The non-spherical particles 246 may be providedin any material, size, shape, and configuration, without limitation. Thesheaths 242 (FIG. 22-22C) may be spherical to facilitate rotation of thecore-sheath nanoparticles 240 prior to resin cure such that thenon-spherical particles may be oriented into at least one commondirection as shown in FIG. 23 and described above with regard to FIGS.22-22C. As mentioned above, dissolution of the sheaths 242 during resincure may result in the shaped or non-spherical particles remaining inthe resin 112.

Step 402 of the method 400 may include applying a mechanical load (notshown) and/or thermal load (not shown) to the composite structure 100containing the shaped or non-spherical particles 246. Mechanical loadsmay include, but are not limited to, tension, compression, shear,torsion, and bending loads, or other types of loads. Thermal loads orthermal cycling of the composite structure 100 may occur as a result oftemperature changes in the composite structure 100 such as a result oftemperature changes in the operating environment of the compositestructure 100 during the service life of the composite structure 100. Asa result of the mechanical loads and/or thermal loads on the compositestructure 100, a crack 116 (FIG. 23) may propagate in the resin 112.

Step 404 of the method 400 may include redirecting the propagation of acrack 116 in the resin 112 using the shaped or non-spherical particles246 as shown in FIG. 23. A crack 116 may preferentially progress along adirection wherein the crack 116 overcomes the local failure strain ofthe resin 112 in response to local stresses resulting from themechanical and/or a thermal load. The shaped or non-spherical particles246 may directly influence the propagation of a crack 116 by alteringthe crack path through the resin 112. In addition, the shaped ornon-spherical particles 246 may indirectly influence the propagation ofa crack 116 by locally changing the resin properties in differentdirections as a result of the presence of the shaped or non-sphericalparticles 246.

Illustrative embodiments of the disclosure may be described in thecontext of a method (not shown) of manufacturing and/or servicing anaircraft, spacecraft, satellite, or other aerospace component.Pre-production, component manufacturing, and/or servicing may includespecification and design of aerospace components and materialprocurement. During production, component and subassembly manufacturing,and system integration of aerospace components takes place. Thereafter,the aircraft, spacecraft, satellite, or other aerospace component may gothrough certification and delivery in order to be placed in service.

In one example, aerospace components produced by the manufacturing andservicing method may include an airframe with a plurality of systems andan interior. Examples of the plurality of systems may include one ormore of a propulsion system, an electrical system, a hydraulic system,and an environmental system. Any number of other systems may beincluded. Although an aerospace example is shown, different illustrativeembodiments may be applied to other industries, such as the automotiveindustry.

Apparatuses and methods embodied herein may be employed during at leastone of the stages of an aerospace component manufacturing and/orservicing method. In particular, a composite structure 100 (e.g., FIG.1), a coating, an injection-molded plastic, and/or an adhesive may bemanufactured during any one of the stages of the aerospace componentmanufacturing and servicing method. For example, without limitation, acomposite structure may be manufactured during at least one of componentand subassembly manufacturing, system integration, routine maintenanceand service, or some other stage of aircraft manufacturing andservicing. Still further, a composite structure may be used in one ormore structures of aerospace components. For example, a compositestructure may be included in a structure of an airframe, an interior, orsome other part of an aircraft, spacecraft, satellite, or otheraerospace component.

Additional modifications and improvements of the present disclosure maybe apparent to those of ordinary skill in the art. Thus, the particularcombination of parts described and illustrated herein is intended torepresent only certain embodiments of the present disclosure and is notintended to serve as limitations of alternative embodiments or deviceswithin the spirit and scope of the disclosure.

What is claimed is:
 1. A composition, comprising: a resin; a pluralityof polymer nanoparticles included in the resin to form a resin mixture;at least some of the polymer nanoparticles are core-sheath nanoparticlesthat each have a sheath encapsulating a core, the core of at least someof the core-sheath nanoparticles being a shaped particle having anon-spherical shape; the sheath is fully soluble in the resin prior toor during curing or solidifying of the resin such that only the coreremains after the resin mixture cures or solidifies to form a curedresin mixture; the shaped particles have the same non-spherical shapeand each have a particle axis, the particle axes of the shaped particlesbeing oriented in a same direction within the resin mixture prior to orduring curing or solidifying.
 2. The composition of claim 1, wherein:the sheath of the core-sheath nanoparticles is generally spherical priorto dissolution of the sheath.
 3. The composition of claim 1, wherein:the resin mixture is included in at least one of the following: acoating, and an adhesive.
 4. The composition of claim 1, wherein theresin and/or the sheath and/or the core are comprised of at least one ofthe following: thermoplastic material including at least one of thefollowing: acrylics, fluorocarbons, polyamides, polyolefins, polyesters,polycarbonates, polyurethanes, polyaryletherketones, polyetherimides,polyethersulfone, polysulfone, and polyphenylsulfone; thermosettingmaterial including at least one of the following: polyurethanes,phenolics, polyimides, sulphonated polymer, a conductive polymer,benzoxazines, bismaleimides, cyanate esthers, polyesters, epoxies, andsilsesquioxanes.
 5. The composition of claim 1, wherein: the polymernanoparticles have a cross-sectional width of 10-200 nanometers.
 6. Thecomposition of claim 1, wherein: at least some of the polymernanoparticles have a cross-sectional width that is different than thecross-sectional width of other polymer nanoparticles in the resinmixture.
 7. The composition of claim 1, wherein: the polymernanoparticles constitute no less than 10 percent by volume of the resinmixture.
 8. The composition of claim 1, wherein: the polymernanoparticles constitute up to 75 percent by volume of the resinmixture.
 9. A composition, comprising: a resin; a plurality of polymernanoparticles included in the resin to form a resin mixture; at leastsome of the polymer nanoparticles are core-sheath nanoparticles thathave a sheath encapsulating a core, the core of at least some of thecore-sheath nanoparticles being a shaped particle having a non-sphericalshape; the sheath is fully soluble in the resin prior to or duringcuring or solidifying of the resin such that only the core remains afterthe resin mixture cures or solidifies to form a cured resin mixture; atleast some shaped particles each have at least one of the followingshapes: oblong, elliptical, cylindrical, tubular, cubic, rectangular,pyramidal, bow tie, toroid, disk, jack, cross, star, dog bone, thinplate with triangle shape, thin plate with square shape; and at leastsome of the shaped particles have the same non-spherical shape and eachhave a particle axis, the particle axes of the shaped particles beingoriented in a same direction within the resin mixture prior to or duringcuring or solidifying.
 10. The composition of claim 9, wherein: theparticle axis of at least some of the shaped particles is orientedparallel to the particle axis of other shaped particles along twodifferent directions.
 11. The composition of claim 9, wherein: theshaped particles are formed of at least one of the following materials:metallic material, polymeric material, and inorganic material includingat least one of ceramics and glasses.
 12. The composition of claim 9,wherein: the sheath of the core-sheath nanoparticles is generallyspherical prior to dissolution of the sheath.
 13. The composition ofclaim 9, wherein the resin and/or the sheath and/or the core arecomprised of at least one of the following: thermoplastic materialincluding at least one of the following: acrylics, fluorocarbons,polyamides, polyolefins, polyesters, polycarbonates, polyurethanes,polyaryletherketones, polyetherimides, polyethersulfone, polysulfone,and polyphenylsulfone; thermosetting material including at least one ofthe following: polyurethanes, phenolics, polyimides, sulphonatedpolymer, a conductive polymer, benzoxazines, bismaleimides, cyanateesthers, polyesters, epoxies, and silsesquioxanes.
 14. The compositionof claim 9, wherein: the polymer nanoparticles have a cross-sectionalwidth of 10-200 nanometers.
 15. The composition of claim 9, wherein: atleast some of the polymer nanoparticles have a cross-sectional widththat is different than the cross-sectional width of other polymernanoparticles in the resin mixture.
 16. The composition of claim 9,wherein: the polymer nanoparticles constitute no less than 10 percent byvolume of the resin mixture and/or the polymer nanoparticles constituteup to 75 percent by volume of the resin mixture.
 17. An injectionmoldable plastic, comprising: a resin; a plurality of polymernanoparticles included in the resin to form a resin mixture; at leastsome of the polymer nanoparticles are core-sheath nanoparticles thateach have a sheath encapsulating a core, the core of at least some ofthe core-sheath nanoparticles being a shaped particle having anon-spherical shape; the core of at least one of the core-sheathnanoparticles is formed of polymeric material; the sheath is fullysoluble in the resin prior to or during curing or solidifying of theresin such that only the core remains after the resin mixture cures orsolidifies to form a cured resin mixture; the shaped particles have thesame non-spherical shape and each have a particle axis, the particleaxes of the shaped particles being oriented in a same direction withinthe resin mixture prior to or during curing or solidifying, the sheathof at least some of the core-sheath nanoparticles having a materialcomposition that improves a toughness of the resin mixture when cured orsolidified.
 18. The injection moldable plastic of claim 17, wherein: thesheath of the core-sheath nanoparticles is generally spherical prior todissolution of the sheath.
 19. The injection moldable plastic of claim17, wherein the resin and/or the sheath and/or the core are comprised ofat least one of the following: thermoplastic material including at leastone of the following: acrylics, fluorocarbons, polyamides, polyolefins,polyesters, polycarbonates, polyurethanes, polyaryletherketones,polyetherimides, polyethersulfone, polysulfone, and polyphenylsulfone;thermosetting material including at least one of the following:polyurethanes, phenolics, polyimides, sulphonated polymer, a conductivepolymer, benzoxazines, bismaleimides, cyanate esthers, polyesters,epoxies, and silsesquioxanes.
 20. The injection moldable plastic ofclaim 17, wherein: the polymer nanoparticles have a cross-sectionalwidth of 10-200 nanometers.
 21. The injection moldable plastic of claim17, wherein: at least some of the polymer nanoparticles have across-sectional width that is different than the cross-sectional widthof other polymer nanoparticles in the resin mixture.
 22. The injectionmoldable plastic of claim 17, wherein: the polymer nanoparticlesconstitute no less than 10 percent by volume of the resin mixture and/orthe polymer nanoparticles constitute up to 75 percent by volume of theresin mixture.
 23. A method of manufacturing a composition, comprising:mixing a plurality of polymer nanoparticles into a resin to form a resinmixture, at least some of the polymer nanoparticles are core-sheathnanoparticles that have a sheath encapsulating a core formed ofinsoluble material, the core of at least some of the core-sheathnanoparticles being a shaped particle having a non-spherical shape, atleast some of the shaped particles each have at least one of thefollowing shapes: oblong, elliptical, cylindrical, tubular, cubic,rectangular, pyramidal, bow tie, toroid, disk, jack, cross, star, dogbone, thin plate with triangle shape, thin plate with square shape, atleast some of the shaped particles have the same non-spherical shape andeach have a particle axis; and orienting the particle axes of the shapedparticles parallel to each other within the resin mixture prior to orduring curing or solidifying; and fully dissolving the sheath of thecore-sheath nanoparticles in the resin prior to or during the curing orsolidifying of the resin mixture in a manner such that the shapedparticles remain oriented in a same direction after the resin mixturecures or solidifies.
 24. The method of claim 23, wherein: the sheath ofthe core-sheath nanoparticles is generally spherical prior todissolution of the sheath.
 25. The method of claim 23, wherein the resinand/or the sheath and/or the core are comprised of at least one of thefollowing: thermoplastic material including at least one of thefollowing: acrylics, fluorocarbons, polyamides, polyolefins, polyesters,polycarbonates, polyurethanes, polyaryletherketones, polyetherimides,polyethersulfone, polysulfone, and polyphenyl sulfone; thermosettingmaterial including at least one of the following: polyurethanes,phenolics, polyimides, sulphonated polymer, a conductive polymer,benzoxazines, bismaleimides, cyanate esthers, polyesters, epoxies, andsilsesquioxanes.
 26. The method of claim 23, wherein: the polymernanoparticles have a cross-sectional width of 10-200 nanometers.
 27. Themethod of claim 23, wherein: the polymer nanoparticles constitute noless than 10 percent by volume of the resin mixture and/or the polymernanoparticles constitute up to 75 percent by volume of the resinmixture.